Continuous tube or bar rolling mill



Dec. 13, 1938. B. BROWNSTEIN 2,140,414

CONTINUOUS TUBE OR BAR ROLLING MILL I 2 Sheeis-Sheet 1 I Filed Sept. 5, i956 Dec. 13, 1938. B. BROWNSTEIN Filed Sept. 5, 1936 Patented Dec. .13, 1938 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to continuous bar or tube rolling mills having a fixed mandrel for use in rolling tubes substantially shown in my prior Patent 2,025,439, granted December 24,

1935, and relates particularly to the formation of the roll passes and the angular relation of the passes to each other.

The present practice in continuous rolling mills for bars and tubes is to provide roll sets disposed alternately in vertical and horizontal position or to dispose these roll sets in planes at an angle of 45 to the horizontal but at right angles to each other, the axes of the rolls in either case being thus 90 apart.

In order to drive either vertical rolls or rolls set at an inclination of 45;to the horizontal pass line, beveled gears must be used, and this is very objectionable in heavy mill work, because beve ed gears are a weak element in the rolling mill drive. Direct driving from motor to pinions and from pinions through spindles is the modern method for driving rolling mills and because of this fact, very few continuous rolling mills for .tubes are in use, and the few that are in use are for very small sizes of tubes. It is impossible to use angularly related shaft sections for transmitting power where the angle is very great, as for instance, at right angles to a horizontal plane or at an angle of 45 to a horizontal plane, for

the reason that when two rotatable bodies are connected-at an angle, the velocity within one revolution varies greatly, when the angle between the roll axis and the pinion stand becomes large and angular strains and stresses are set up in the connections which consume powerand create wear and tear on the rolls and spindles. As the angle increases, the variation in rotation per revolution increases as does the power consumption. When the power consumed at the rolls 0 and spindle connections becomes equal to the power input, rotation ceases and that angle at which the spindle and roll ceases to operate is called the locking angle. Rolls set at an angle of to a horizontal plane cannot be driven by spindles connected by universal couplings to pinion-carrying shafts, because this angle is a locking angle and hence beveled gears must be used. Beyond an angle of 25 to a horizontal plane, the power consumption becomes excessive and trouble manifests itself in the driving parts.

One object of my invention, therefore, is to eliminate the use of vertical rolls, with their consequent.wear and consequent necessity of using beveled gears for driving and permit the use of a direct drive from the motor to pinions and from pinions through inclined shafts to the rolls and thus putting the continuous rolling mill for heavy rolling of bars and tubes on the same footing as the continuous rolling mills for plates, sheets or 6 strips having horizontal drives, and to this end, I dispose the roll axes of all rolls having a reduction per pass of 15% or less in a horizontal plane and all those rolls having a reduction per pass in excess of 15%, I dispose at an angle to 10 the horizontal plane varying from 1 to 25 maximum per pass. This inclination of the roll axes depends upon the reduction per pass. As the reduction increases, the inclined angle increases until it reaches a maximum of 25. 5

In all continuous bar or tube rolling mills having alternate vertical and horizontal rolls, it is necessary to place the line or plane of greatest reduction of a pass at an angle of 90 to the line or plane of reduction of the previous or suc- 20 ceeding pass in order to enable the bar or tube being rolled to enter the second pass or, in other words, so that the plane or line of greatest reduction (which is the minor transverse axis of ,the bar or tube) mayenter within the major axis 25 of the next adjacent pass, and it is necessary to use twist guides to rotate the bar or tube trans- Versely through an angle of 90. Twist guides, however, cannot be used successfully in rolling tubes except for the first three or four passes, 30 because the wall of the tube is not thick enough to provide proper bearing surface for the twist guides to work on while twisting the tube sections.

A further object, therefore, is to so form the 35 rolls that the dividing center line or plane of all the roll passes, except the last pass, is at an angle with the roll axes, irrespective of the shape of the groove in the periphery of the rolls and whether this is used for making round, square, rectan- 40 'gular, triangular or oval bars or tubes. Thus all the rolls, except the last finishing rolls, each have a large diameter on one side of the roll groove and a small diameter on the opposite side,

-the large diametered portion of one roll facing 45 the small diametered portion of the opposed roll so that the plane or line of greatest reduction is at an angle to the axes of the pair of rolls of from 89 to A further object is to so dispose and form the 50 rolls of any one pair relative to the next adjacent pair that when reduction is less than 15%, the

angle between the planes of greatest reduction of the pass and theaxes of the rolls is from 60 to and that when reduction is over 15%, the I angle between the plane of reduction and the I axes of the rolls is increased up to 90, and in this connection to dispose the rolls of each pass so that the axes of one set or pair of rolls has an opposite angular relation to the axes of the next adjacent pair of rolls, the angles alternately being right hand and left hand and the axes of each pair of rolls being disposed at an angle with a. horizontal plane or pass line varying from 1 to 25 maximum, depending upon the nature and form of the material rolled. It is to be understood that for reducing upto 15% maximum per pass, all the roll axes are disposed in a horizontal plane, but that for reductions greater than 15% per pass, that is, for heavy work, all roll centers or axes are disposed at an angle with a horizontal plane or pass line varying from 1 to 25 maximum, as before stated. Due to the roll axes or centers being set either horizontally or at an angle not greater than 25 to a horizontal plane, the rolls can be driven by horizontal or angular connecting spindles in turn connected to or driven from pinions or horizontal shafts. The connected roll spindles will thus divide the angle which the roll centers or axes make with the pinion axes, thus reducing the driving angle of the roll spindles in half and: securing a smoother drive.

A further object is to so form and dispose the complementary rolls of each pass that no fins will be formed by a succeeding pass and a perfectly rolled bar or tube is delivered from the pass.

A further object, is to provide guide rolls between the passes so constructed that they will act as twist guides for the first three or four passes and as straight guides for the last passes.

Other objects will appear in the course of the following description.

My invention is illustrated in the accompanying drawings wherein:

Figures 1 to 5 are elevations showing successive roll passes;

Figure 6 is an elevation showing the final roll D B 1 Figure 7 is an elevation of a pair of inlet roller guides such as are disposed between each pair of roll passes, the inlet guide shown in Figure '7 having the grooves of the rollers arranged to conform to the shape of the bar or tube as it travels from the pass shown in Figure 1 to the pass shown in Figure 2;

Figures 8 to 13 illustrate diagrammatically the several roll passes shown in Figures 1 to 6, the bar or tube being shown in section, the axes of the rolls in Figures {3 to 13 being disposed in horizontal planes to prevent confusion.

In Patent 1,912,966, granted to me on June 6, 1933, I disclose a process of forming a tubular ingot. This hollow ingot is placed upon a fixed mandrel, as disclosed in my Patent 2,025,439, previously referred to, and drawn out over this mandrel to elongate the tube and reduce its diameter as it travels continuously in one direction and through the several roll sets, now to be described.

It is to be noted from all the figures of the drawings in the instant case, except Figures 6, 13, that the rolls shown have a small diameter and a large diameter, as previously referred to, and that the large diameter of one roll confronts and approximates the small diameter of the pposed roll, so that the line oi. greatest reduction is at an angle to the roll axes. When the reduction of all. the rolls of a continuous rolling mill is not greater than 15% per pass, then all the rolls are horizontal. But ii! the reduction in any one pass or several passes is greater than 15%, then these rolls must be placed at an angle to the horizontal, the angle depending upon the reduction per pass. As-the reduction increases, so does the angle between the roll axes and the horizontal increase, and vice versa. All the rolls of a continuous rolling mill can be made to have the same percentage of reduction per pass and their angle between the horizontal and their axes will be the same, or constant. If 15% or less, the angle will be zero, and if greater than 15%, the angle will be 1' and up to a maximum of 25 per set of rolls. In other words, the reductions can be made constant for all passes of a continuous rolling mill, or they can be made to vary per pass from 1% to 40 or 50% per. pass and the angles between their axes and the horizontal will vary for each set 01' rolls.

Figures 1 to show a series of five passes, each pass being formed or defined by a pair of rolls l0 and H having parallel roll necks l2 and I3, respectively. All of the several pairs of rolls have the same general form and each roll has a small diametered portion l 4,.a large diametered portion l5 and a roll groove it which extends in a transversely concave curve from the periphery of the large diametered portion 15 to the periphery of the small diametered portion I4 to thus define the pass designated I! in Figure 1. It will be noted in these figures that each pair of rolls defines a roll pass which is generally elliptical in form and that a plane aa, Figure 1, cutting the center of the pass and approximately cutting the junction between the part M of one roll and the portion ii of the other roll extends along the major diameter of the pass and that the passes are successively smaller from the first passto the fifth pass This is secured by making the groove I 6 successively narrower and successively increasing the diameters of each pair 01' rolls along the middle plane of the grooves.

It is reiterated that in these several figures, except Figure 6, the line of greatest reduction is at right angles tothe line a-a of Figure 1 and line a-a of Figure 8.

It is to be particularly noted from Figures 1 and 2 that the line b-b parallel to the rotative axis of the rolls l0 and II and intersecting the center of the roll pass I I is at an angle of approximately 15 to a horizontal plane h-h passing through said center. This angle between the line b-b, which is the pass line and the horizontal plane h-h may be anywhere from 1 to 25 but should not exceed 25 for the reasons heretofore stated. Due to the roll axes being set horizontally (for a reduction of not more than 15% per pass) or at an angle not more than 25, the rolls can be drivenby horizontal or angular connecting spindles, connecting with two pinions disposed on horizontal shafts which in turn are connected to reduction gear drives or the spindles may be connected directly, without reduction gear drives, to adjustable speed motors; thus are set in their proper places with respect to their passes, but in my construction, the connecting roll spindles will divide the angle that the roll axes make with the pinion centers or axes, thus reducing the drive angle of the spindles in half and securing a smoother drive as before stated. In my arrangement of rolling mill rolls with the axes of the rolls disposed at an angle of 25 to a horizontal plane, the axes of any two adjacent rolls would be disposed at an angle of with relation to each other. With the axes of the rolls set at 15 from a horizontal plane, the axes of the rolls will be apart and-obviously, if the axes of the rolls are disposed at an angle of 1 with'relation to the horizontal plane,

the angle between the axes of adjacent rolls would be 178 apart. In my arrangement of rolling mill rolls, the major axis of all the passes, except the last. round pass shown in Figure 6, varies from 60 to 90 with relation to each other and so do the minor axes. In reductions up to about 15% in which the roll axes are set in horizontal planes, the minor axes of the several passes as they are modified by the angle of the pass, will just about allow the bar or tube to enter the different passes without any trouble, but when the reduction is increased beyond 15% per pass, the angle between the minor axes of two adjacent passes must also be increased in order to enable the bar or tube to enter the next pass and not cause any trouble. The reason for thisincrease in the angle is due to the fact that the major transverse axis of the bar or tube, modified by the angle as it leaves the pass, is not reduced enough to allow it to enter the minor axis of the next pass, therefore, the angle of the roll passes to each other must be increased until the bar or tube will enter the different passes during the rolling operations. Under no circumstances can a reduction be made where the major axis of a succeeding pass is smaller than the minor axis of the preceding pass. This is fundamental. Thus as shown in Figures 10 and 11, if the line X in Figure 10 (which is tangential to the curvature of the tube, section and parallel to the axis of the rolls and equal in length to the distance between the projection lines of the tube section ends) is greater than the length of the same line X on the next succeeding pass, Figure 11, then the angle of the roll axes of such succeeding pass shown in Figure 10 to the horizontal must be increased until the distance between the projection lines of thetube section is less than the length of line X.

My roll passes are so designed that they can operate at an angle of 60 to 90 between the roll pass centers or axes when the roll axes are horizontal or make an angle with the horizontal from zero to 25 maximum, depending upon the amount of reduction per pass.

It is to be particularly noted that in my construction, as shown in Figures 1 to 5, the roll body or portion M of smallest diameter on one .roll confronts the face of the roll body or portion l5 of largest diameter on the opposed roll. In my construction, there are, therefore, two portions of this roll body which define the groove in the rolls. It will be seen that with this construction, the large diametered part l5 of the roll moves the metal along the pass while it is under the least pressure and moves it very nearly at right angles to the body of the opposed roll. By this means and by the angular relation which the rolls bear to the horizontal plane, I am enabled to produce a perfectly rolled baror tube without fins. are a great trouble and a great source of rejection, for the reason that these fins weaken the Fins found in the walls of tubeswall of the tube as they are cold compared with the body of the tube and have scale on their surfaces, and when these conditions occur, welding cannot take place. These fins, if formed,

cool very quickly and this hard metal fin is rolled into the body of the tube in the next pass. These fins are often produced as the rolling operations are continued in a certain apparatus and produce a tube with a wall full of fins which is rejected by the inspection department.

The dimensions and form of any of my improved roll passes depend upon the dimensions of the bar or tube to be rolled and the percentage of reduction per pass. The large dimension of the tube to be rolled governs the large diameter of the pass along the dividing center line 11-41 (Figure 1) of the groove of the first pass. The diameter of the smaller portion i4 is fixed by the percent reduction per pass and the large diameter l5 of all the passes, except the first pass, is fixed by the small diameter of each pass. The distance between the large and small diameters of the rolls is in turn fixed by the angle that the large diameter makes with the roll center, that is, with the axis of the roll. when the reduction per pass is greater than 15%, the distance between the large and small diameters becomes reduced in greater proportion than the largediameter of the groove and the bar leaving the first pass cannot, therefore, enter the second pass, hence, as stated before, it becomes necessary to increase theangle between the dividing center line a,-a of the groove or center pass line and the line 11-!) which is parallel to the longitudinal axes of the rolls. This angle of the dividing center line a--a (Figure 1) cannot be increased in the roll body because it is fixed. by the reduction of the pass, therefore, the roll centers or axes 'must be placed at an angle to the horizontal pass lines 12-71. in order to increase" the angle between the pass line and the line It should be particularly vborne in mind that the angle of the roll sets do not need to be all the same, in other words, the angle of any one roll set with relation to the pass line may vary from the angle of the preceding or succeeding roll set. The angle of each pass or set of rolls will be governed by the percent reduction and the. form of the pass. Some rolls may be horizontal,-

Ilia and Ila in Figure 6, may have their axes disposed at an angle of from 1 to 25 to a horizontal plane, as described for the preceding roll sets, but the grooves Ilia in this last roll set are semi-circular in crosssection and, oi course,

smaller in diameter than the width of the grooves H5 in the preceding roll set shown in Figure 5.

These rolls Na and Ila give, therefore, the final reduction and form to the bar or tube.

Between each roll set is disposed a pair of guide rolls l8 and I9, as shown in Figure '7,"

which are disposed for rotation around vertical axes, the grooves in these rolls being shaped to conform properly to the shape of the grooves of the preceding roll pass, or in other words, to the form of the material as it is delivered from thatpass, each roller inlet guide groove being made up of approximately half of the grooves or pass of the top and bottom rolls of the preceding pair. The guide rollers shown in Figure '7 have the grooves so formed as to conform properly to the I have found that.

. through the several passes.

. x cross-section of the tube as it is delivered from the pair of rolls shown in Figure In Figures 8 to 13, I haveillustrated fragmentary elevations of the roll sets shown in Figures 1 to 6, and show in section the form given to the tube being treated as it is rolled through the several passes. In these Figures 8 to 13, however, the rolls are not shown as canted in opposite directions with relation to each other as in Figures 1 to .6, it being understood that these Figures 8 to 13 are merely designed to illustrate the cross-sectional form of the tube as it travels The line indicating the major diameter of the pass formed between the grooves of the first pair of rolls is indicated in Figure 8 as well as the horizontal plane hh and the pass plane b-b which is parallel to the axes of the rolls.

It is reiterated that while I have illustrated all of the rolls as disposed with their axes at the same angle to a horizontal plane (this angle being shown as 15 though it may be anywhere from 1 to maximum) yet each pair of rolls may have its axesat a diiferent angle from the axes of the next adjacent pair; or all of the axes may be horizontal (where the reduction is less than 15% per pass) or the angle of the roll axes may progressively increase from the first pass to the last from 0 to 25 maximum.

filhe percentage reduction per pass is fixed by the size of the stock, bar, bloom or the hollow ingot, the number of rolls or passes in the continuousrolling mill, and the final size of the rolled bar, billet or tube. These three factors and the revolutions of the rolls govern the reductions per pass and also govern the total reduction necessary in order to produce the finished bar, billet or tube. The guide rollers l8 and I! may be used as guide rollers rotating on vertical axes and making an angle of 90 with the horizontal irrespective of the angle which the roll axes make to thehorizontal plane. When these guide rollers I8 and I9 are used as twist guides, their axes of rotation can be vertical (90 to the horizontal) or at an angle more than 90to the horizontal irrespective of the angle the roll axes make to the horizontal.

As I have stated in the first paragraph of this specification, this invention relates to tube rolling mills having a fixed mandrel, as shown in my prior rPatent No. 2,025,439. This fixed mandrel is used in rolling tubes from ingots formed as disclosed in my Patents Nos. 1,913,966 and 1,912,965, issued June 6, 1933. It was the general object of these prior patents to eventually produce tubes froni ingots weighing from 10,000 to 25,000 poundseach and to make these tubes in all sizes up to O. D. and larger in lengths from 100 feet to 300 feet ,or more. The rolling operation for tubes of this size and of this length is a problem for many practical reasons. The major reasons are as follows:

First, the practical limited length of the man drel bar; 1

Second, the total length of the continuous rolling mill to meet the limited length of the mandrel bar;

Third, the problem of turning each section of each pass so that the major axis of the rolled sec: tion of the preceding pass will enter the minor axis of the succeeding pass which is the fundamental principle in the art of rolling; J

Fourth, cooling. thev ingot during the rolling operation to prevent the hollow ingot or tube mill operation because the rolled ingot .bar to a practical limit for int? the tube must from sticking to the rolling plugs of the fixed The minimum reduction that can be used under.

these circumstances is 25% per pass and the maximum reduction be from to per pass.

As an example, to produce a tube 10%" O. C.,

10" I. D. and 300 feet long. requires a hollow ingot (such as is produced by mechanism constructed in accordance with the patents above referred to) 30" 0. D., 8 feet long weighing 12,800 pounds. This requires 10 reducing passes with reduction of 32.57% per pass and two finishing.

passes, making a total of 12 1 h A continuous rolling mill with 12 roll stands will be about 90 feet long, not charge table. The mandrel bar, under these circumstances, will be 110 feet long, this mandrel.

bar being constructed in accordance with my Patent No. 2,025,439.

In the usual rolling mill, in order to turn a solid roll section, as it leaves the first pass and before entering the scond pass, it is necessary to.

use twist guides or the roll stands are placed far apart with a long table between them to allow the rolled section to be turned freely 90 before it enters the second pass. These methods cannot be used in connection with my hollow ingot process. first, because the ingot when it is twisted becomes distorted internally, causing the section between the roll stands to get out of round and rendering them unable to slip over the rolling plug of the next succeeding pass. Second, when twisting the rolled section, the mandrel bar is also twisted, because it is held firmly by the metal of the tube withgreat resisting force and 10 twisting operations, each of 90, would soon ruin the mandrel bar. Such mandrel bars would be too expensive to replace for every rolling operation. There would also be a great delay in would stick to the mandrel bar and the mill would have to be opened up as regards the rolls and guides. destroying the whole set-up of the mill.

Again, in rolling mill operations, a great quantityiof water is used to cool the rolls and the guides as well as for breaking up the scale form. Hence the rolled section cools rapidly ,andvthis causes shrinkage in sectional area so that it becomes smaller in diameter and is thus unable to slip over the rolling plug such as used with the mandrel bar forming the subject-matter of my prior patent before referred to. A cobble is the result. Therefore, be kept down to as few stands as possible in order to avoid this trouble and avoid mill delay. Because a small number of stands is used, the reduction must be made large per pass in order to complete the rolling when the. tube leaves the last stand.

From the previous statements; it will become clear that: a. Large reductions per pass must be made in order to keep the length of the mill and mandrel and low bperating costs.

B. The hollow ingot which is being formed not be twisted but some other continuous operation counting the delivery or disthe length of the mill must means must be found to meet the fundamental requirement for a 90 turning of the hollow ingot beforeentering each succeeding pass.

I have fulfilled these fundamental requirements in the finally developed roll passes illustrated and described herein and only after many years of research and actual experimental work with small continuous rolling mills. .By reason of the form of the roll passes and the inclination of the rolls with reference to each other, I can secure reductions of from 15% to 50% per pass.

What is claimed is:

1. A continuous tube rolling mill, including a series of pairs of complementary rolls, each pair of rolls having their axes of rotation parallel to each other inclined at an angle to a horizontal plane ranging from 15 to not more than approximately 25, the plane of the major axis of the-pass of one pair of rolls being disposed at an angle of from 60 to 90 to the plane of the major axis of the pass of the next adjacent pair of rolls, each pair of rolls having their rotative axes inclined in a direction opposite to the inclination of the rotative axes of the next adjacent pair of rolls, each roll of each pair of rolls, except the last pair, having a large diametered portion and a small diametered portion separated by a groove, the large diametered portion of one roll facing toward and confronting the small diametered portion of the opposed roll and defining an elliptical pass, each roll of the last pair of rolls of the series having a medial groove and portions of the same diameter on each side of the groove, the passes formed between the rolls of each pair being gradually smaller from the first pair of rolls to the last pair of rolls.

2. A continuous tube rolling mill, including a series of pairs of complementary parallel rolls, the axes of each pair of rolls being inclined at an angle to a horizontal plane ranging from 15 to approximately 25, the axes of any one pair of rolls being inclined oppositely to the axes of the next adjacent pair of rolls, each roll of a pair having a large diametered portion and a small diametered portion separated by a groove and defining an elliptical pass, the large diametered portion of one roll of a pair facing the small diametered portion of its companion roll whereby the pass defined by the opposed rolls has a major diameter intersecting the approximating faces of the rolls, the rolls being disposed at such an angle with relationto each other that the major diameter of the pass of one pair of rolls is disposed at an angle of from 60 to 90 to themajor diameter of the pass of the next "adjacent pair of rolls.

3. A continuous tube rolling mill, including a series of pairs of complementary rolls, the axes of each pair of rolls being parallel with each other inclined at an angle to a horizontal plane ranging from 15 to approximately 25, each roll of a pair having a large diametered portion and a small diametered portion separated by a groove and defining an approximately elliptical pass, the large diametered portion of one roll of a pair facing the small diametered portion of its companion roll whereby the pass defined by the opposed rolls has a major diameter intersecting the approximating faces of the rolls, the axes of any one pair of rolls being disposed at such an angle to the axes of the next adjacent roll that the major diameter of the pass of one pair of rolls is disposed at an angle of from 60 to 90 to the major diameter of the pass of the next pair of rolls, the axes of one pair of rolls being oppositely inclined to the axes of the next adjacent pair.

4. A continuous tube rolling mill, including a series of pairs of complementary grooved reducing rolls having parallel rotative axis, the grooves of each pair defining a pass; each roll having a large diametered portion and a small diametered portion whereby the plane of greatest reduction and therefore the minor diameter of the pass is at an angle to the axes of the rolls and defining an elliptical pass the rotative axes of each pair of rolls being disposed at an angle to the horizontal plane and the rotative axes of any pair of rolls being oppositely inclined to the rotative axes of the next adjacent pair; the angular relation of the major diameter of any one pass to.

the major diameter of a succeeding pass being such that a projection of the major diameter of a preceding pass is less in length than the proiection of the major diameter of the next succeeding pass.

BENJAMIN BROWNS'I'EIN. 

